Sinker electrode choice for Tungsten, MolyBdenum, Niobium, Tantalum, Refractories

[claya]

Can someone suggest electrode options for the refractory materials? Someone recommended Copper but which copper (Pure, C110 or C145 Tellurium)?

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[mactec54]

Can someone suggest electrode options for the refractory materials? Someone recommended Copper but which copper (Pure, C110 or C145 Tellurium)?

What material are you burning

[claya]

What material are you burning

All of the above. At the moment : Niobium and Tungsten.

[claya]

What material are you burning

Also. The electrodes are VERY small 0.02" x 0.117" (Area= 0.002in-sq) and 0.02" x 0.03" (A=0.006"in-sq). What is the max roughing amps I should use to minimize wear? Test cuts with copper @15.5A are wearing more than I like. @9A the burn is too long & still have too much wear.

[mactec54]

Also. The electrodes are VERY small 0.02" x 0.117" (Area= 0.002in-sq) and 0.02" x 0.03" (A=0.006"in-sq). What is the max roughing amps I should use to minimize wear? Test cuts with copper @15.5A are wearing more than I like. @9A the burn is too long & still have too much wear.

Yes, copper will wear a lot even with normal use, can be good for finishing, can you grind up some carbide might work out better or some Copper Tungsten machines quite well

10A would be about right depending on your machine, long on time sort off time, watch for contamination, you need good flushing for small detail work like this.

Negative Polarity is sometime used to EDM these materials, this can also destroy the electrode. start with low amps if you try this.

[claya]

Carbide as a roughing electrode? I am using Copper-Tungsten as a finish electrode @ 2A. The copper roughers last better at 4A, but the burn is very slow. 12on/18off. Pulse 15down/20up.

I am getting a burr/short taper at the bottom of the 0.160" deep thru slot. The width is 0.024" for most of the slot, but then suddenly tapers to 0.022". I suspect the taper is from poor flushing once the electrode breaks thru the wall. I can see a slight taper on the finish trode. Are there settings I can alter to eliminate the taper? I cannot burn deeper. And increasing to 5A does not do anything. The finish trode is 0.0215". Target slot is 0.023" min.

Yes, copper will wear a lot even with normal use, can be good for finishing, can you grind up some carbide might work out better or some Copper Tungsten machines quite well

10A would be about right depending on your machine, long on time sort off time, watch for contamination, you need good flushing for small detail work like this.

Negative Polarity is sometime used to EDM these materials, this can also destroy the electrode. start with low amps if you try this.